Devices of this type are used for the interferential measurement of lengths, angles, path differences or velocities with the aid of a dual-beam interference arrangement.
In dual-beam interferometers corresponding to such arrangements like Michelson interferometers, Mach-Zehnder interferometers or the like, the phase or path difference change between the two partial beams connected with the respective measurement process does not yet provide any information regarding the sign of these phase or path difference changes or the sign of the speed of change. This information can be additionally obtained by means of various known methods and devices and evaluated by means of known measuring techniques. The underlying principle of these measuring techniques is that phase-shifted, interlinked sinusoidal signal pairs, such as those derived from interference phenomena, permit a directional discrimination.
The properties of the known interferometers with which such signal evaluations are performed are unsatisfactory for several reasons, depending on their application. Portions of light which return from the interferometer to the laser light source interfere with some of the instruments. With other apparatus it is virtually impossible or only possible with a great amount of effort to generate any modulation periods which have mutual prescribed phase differences. When generating signals which are phase-shifted with respect to each other, simple methods are lacking for simultaneously obtaining optical push-pull signals which stabilize the operating points of the signal amplifiers.
Interferometers as described above usually are constructed as follows: besides a beam splitter and two retro-reflectors, a number of optically polarizing components are required for the generation of useful phase-shifted signals (0.degree., 90.degree., 180.degree., 270.degree.) and to make a determination of direction possible in this way. The optically polarizing components are large, expensive and their adjustment is elaborate.
With the above-description of prior art interferometers in mind it is an object of the present invention to create a device for interferential measurements of any arbitrary type whose measuring techniques are satisfactory and which is designed in a particularly simple manner.
Another object of the present invention is to simplify the construction of interferometers by combining the functions of beam splitting and interferentially combining beams in one element.